sd_spi.h

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#ifndef STAR_SD_SPI_H
#define STAR_SD_SPI_H
 
/*
 * Portable pieces of the SD-card SPI protocol (SD Physical Layer Simplified
 * Specification, SPI mode), used to probe the ZDSD01GLGEAG SD NAND (U10).
 * No HAL: the board layer moves the bytes, these build and check them.
 */
 
#include <stdbool.h>
#include <stdint.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
#define SD_CMD0_GO_IDLE 0U
#define SD_CMD8_SEND_IF_COND 8U
#define SD_CMD10_SEND_CID 10U
#define SD_CMD55_APP_CMD 55U
#define SD_CMD58_READ_OCR 58U
#define SD_ACMD41_SD_SEND_OP_COND 41U
 
#define SD_CMD8_ARG 0x000001AAU   /* 2.7-3.6 V, check pattern 0xAA */
#define SD_ACMD41_HCS 0x40000000U /* host supports high capacity */
 
#define SD_R1_IDLE 0x01U
#define SD_R1_ILLEGAL_COMMAND 0x04U
#define SD_DATA_TOKEN 0xFEU
#define SD_OCR_CCS 0x40000000U /* card capacity status: SDHC/SDXC */
 
/* CRC7 (x^7 + x^3 + 1) over len bytes, as used by commands and the CID. */
uint8_t sd_crc7(const uint8_t* data, uint8_t len);
 
/* 6-byte command frame: 01 index, 32-bit argument, CRC7, end bit. */
void sd_command_frame(uint8_t out[6], uint8_t index, uint32_t argument);
 
/* R1 is the first byte with bit 7 clear; 0xFF means "not yet". */
static inline bool sd_is_r1(uint8_t byte) {
    return (byte & 0x80U) == 0U;
}
 
/* CMD8 R7 trailer (4 bytes after R1): voltage accepted and pattern echoed. */
bool sd_r7_ok(const uint8_t r7[4]);
 
/* CID register (16 bytes): byte 15 must be CRC7(bytes 0..14) << 1 | 1, and
 * the contents must not be uniform 0xFF/0x00 (a dead bus). */
bool sd_cid_ok(const uint8_t cid[16]);
 
#ifdef __cplusplus
}
#endif
#endif